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Visual Six Sigma: Making Data Analysis Lean by Leo Wright, Mia L. Stephens, Philip J. Ramsey, Marie A. Gaudard, Ian Cox

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8.5. Uncovering Relationships

With reliable measurement systems in place, the team now embarks on the task of collecting meaningful process data. The team members collect data on all batches produced during a five-week period. They measure the same variables as were measured by the crisis team, with the assurance that these new measurements have greater precision. The data are presented in the JMP data table VSSTeamData.jmp.

Carl's analysis plan is to do preliminary data exploration, to plot control charts for MFI and CI, to check the capability of these two responses, and then to attempt to uncover relationships between the Xs and these two Ys. He keeps his Visual Six Sigma Roadmap, repeated in Exhibit 8.34, clearly in view at all times.

Figure 8.34. The Visual Six Sigma Roadmap

8.5.1. Visualizing One Variable at a Time

To clear his workspace, Carl first closes all open windows in JMP, and then opens VSSTeamData.jmp. As he did for the crisis team's data, Carl's first step is to run Distribution for all of the variables except Batch Number. He selects Analyze > Distribution and adds all 11 Xs and Ys. Once he clicks OK, Carl saves the script for this report as Distribution.

The first five histograms are shown in Exhibit 8.35. Carl and his teammates note the following:

  • MFI appears to have a mound-shaped distribution, except for some values of 206 and higher.

  • CI is, as expected, ...

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